Specifications

Chapter 7. Troubleshooting 175
frame voice <x> Changes the voice DLCI to the specified number x.
frame stats Shows LMI statistics.
For a frame stats example, see page 204.
If the voice gateway is a Jetstream gateway, the following commands are available:
voice l2stats Shows AAL2 statistics for control messages.
voice l2clear Clears the AAL2 statistics to 0.
The following commands allow you to trace all signaling cells sent and received and all encoding changes for
voice ports.
voice lestrace 1 Enables trace messages to the console.
voice lestrace 0 Disables trace messages to the console.
voice lestrace Displays trace messages.
To see the CRC and line errors for SDSL, enter:
sdsl stats
For an sdsl stats example, see page 307.
The dsp debug commands are shown in Voice Router Debug Commands, on page 183.
Adjusting the Jitter Buffer
The jitter buffer shapes data to overcome the problem of latency, that is, the time delay between packets of voice
data that can cause gaps in or loss of traffic in a voice call. A command is available that allows you to adjust the
size of the jitter buffer. The command is as follows:
dsp jitter [<milliseconds>]
milliseconds Length of the jitter buffer in milliseconds (0 - 60).
To display the current jitter buffer, enter the dsp jitter command without its parameter. For example:
# dsp jitter
Jitter Buffer: 15 ms
usage: dsp jitter <milliseconds 0-60>
Use this command if you get what sounds like voice playout underruns under full network loading. Increase the
buffer size until the problem is corrected. However, do not set the buffer unnecessarily large because that would
introduce unnecessary latency.
The jitter buffer should be set to the best estimate of the effective worst-case jitter in the voice-packet arrival time
from the voice gateway. Be aware of the granularity of the setting: for G.711 voice compression, only integer
multiples of 5.5 ms can be realized; for G.726, only integer multiples of 11 ms can be realized. Thus, the
following table illustrates the difference between the value you specify and the actual holding time for G.711 and
G.726. The numbers in parentheses are the number of voice frames held in the jitter buffer.